Process for decomposing silicates of magnesium.



LOUIS L. JACKSON, OF NEW YQRK, N. Y., ASSIGNOR OF ONE-HALF TO ODUS C. HORNEY, 1

OF NEW YQBK, 1\T. Y.

PROCESS FOR DECOMPOSING SILICATES 0F MAGNESIUM.

No Dgawing'.

I To all whom it may concern:

Be it known that I, LOUIS L. Jackson, a

citizen of the United States, residing at such as magnesiumsulfate, from such-abundant silicates as talc aand soapstone, the

latter being available in large quantities as, a waste product at the soapstone quarries.

It is .known that of the many varieties of natural silicates of magnesium, some are decomposed by dilute acids, others by heat.-

ing for a consider able time with compara tively concentrated acids, vahile many are described'as not attacked by acids. In the last mentioned class occurs some of the most a common silicates, e. g. soapstone (talc).

It isalso known that if talc (metasilicate of magnesium, 'H,Mg,Si,O is intensely ignited over a product boiled with a solution of sodium carbonate, about 15% of SiO (about one quarter of the entire silica content) goes into solution as sodium silicate, and an insoluble product is left to which the formula MgSiO has been ascribed. The solution of sodium carbonate has no action on the tale before ilglnition. Acids are also without action on t e talc before ignition; but the art discloses noinformation as to the action of acids on the insoluble product left after boiling with the solution of sodium carbo- Y nate.

I have found that'if those natural silicates, such as talc, soapstone, chrysolite, etc., which are insoluble, or with difliculty soluble, in acids, are heated at a relatively low temperature with a large excess of caustic alkali, they are decomposed into an alkaline silicate and a silicate of magnesium which is V readily soluble in acids, even in very. dilute acids (for example, 1% sulfuric acid), or even diluted organic acids hke acetic acid.

Specification of Letters Patent.

the decomposition blast lamp and the ignited" Patented Jan. 22, rate.

Application filed January 19, 1917. Serial No. 143,242.

In the case of soapstone the reaction appears to be as shown by the following equation:

' To get satisfactory results at a comparatively low temperature it is necessary to use caustic alkali, not carbonate of an alkali,

i and to use the caustic alkali in-large excess, more than twice what is required by theory to combinewitlr-the silica which is removed as alkaline silicate. For example: using twice the theoretical quantity of caustic alkali and heating even as high as 600 C. for two hours, only about one half of the soapstone is decomposed; while by using four times the theoretical amount, almost complete decomposition may be obtained in the same time at 350C, or even at a lower temperature. As the caustic alkali is recovered and used over again, there is no objection to using this large excess.

'Althou h good decomposition can be obtained be ow 350 C., the solution of magnesium salt obtained from the productv heated much below that temperature contains considerable iron, while the product obtained at 350 C(or higher will yield a solution almost free from. iron, if proper care in the additionof the acid is observed.

As indicated above, good results can be ob.-' tained at temperatures much above 350 C., but I prefer to work at about the latter temperature. I

Working in a small we it is conven ent to use fused caustic a ali, adding ust enough water to cause thecaustic alkali to melt at any convenient temperature, say 150 0., then stir in the powdered sillcate and raise the temperature to the desired point. In manufacturing practice the caustic v alkali would be recovered in dilute solution, not over 10%, and would be concentra and used over again. The example given below is in accordance with the manufacturing practice.

parts of powdered soapstone are stirred into a hot solution of caustic soda, as concentrated as it is practicable to get inents selected from the large number-made made soluble 24.50 parts.

it, and representing about 80 parts of sodium hydrate, and the mass is then subjected to a heat of about 350 C. for about two hours. The product is extracted with water to rea move the alkaline silicate and the excess of caustic alkali. 1

The caustic alkali is recovered from the filtrate and washings in' any desired manner and the dilute'solution of caustic concentrated andused over again.

The residue from this washing consists essentially of a silicate of magnesium. This is suspended in water and sufficient acid added to combine with the magnesium. Any acid may be used that will give a soluble magnesium salt. The magnesium salt is recovered from the solution by filtration.

The residue from this filtration, which consists essentially of silica in a very finely divided state mixed with hydrated ferric salt. The magnesium salt may be recovered from the solution so obtained.

Further data with respect to two experi- [are given below.

1. Soapstone 100 partsysodium hydr oxid 80 parts. 'Silica'dissolved'1322 parts; MgO

.2; Asbestoslsocalledt apparently Cana- I dian chrysotile) 100 parts; sodium hydroxid oxid, is washed, and the washings are joined with the filtrate containing the magnesium- 80 parts. Silica dissolved 7.5 parts; MgO made soluble 28.06 parts.

Having now fully described my invention, what I desire to claim and protect by Letters Patent is v 1 The process, of decomposing those silicates of magnesium which are resistant to the action ofacids, which consists in heating an admixture of the silicate and a hy drate of an alkaliimetal, and treating the insoluble part of the product with an acid.

' 2. The process of decomposing those silicates ofmagnesium which are resistant 'to the action of acids, which consists in heating an admixture of the silicate and a hydrate of an alkali metal, thereby forming an alkaline silicate and an insoluble product, separating out the alkaline silicate, treating the insoluble residue with .an acid to de-- compose the same, separating out the mag nesium salt, washing the residue, and jo1ning the washings and the magnesium salt sofsepa-rated out. n

3. The process of decomposing soapstone which consists in heating an admixture of soapstone and sodium hydroxid, separating out the dissolved silica, and treating the insoluble residue with a dilute acid.

In testimony of which invention, I have hereunto set my hand, at New York city,

on this 15th day of J anuary,-1917.

' LOUIS L JACKSON. 

